Spinothalamic tract cells, identified by antidromic activation from the contralateral brainstem, are being examined for convergence of input from visceral and somatic afferents. Visceral and somatic input to spinothalamic tract cells is being tested for reciprocal inhibitory interaction. Both spinothalamic tract cells and other neurons in the thoracic spinal cord are being examined for activity elicited by electrical stimulation of afferent C-fibers in the greater splanchnic nerve. Interactions between somatic and visceral A-beta afferent input onto neurons in the dorsal column nuclei are also being studied. Tract cells in the dorsal column nuclei are identified by antidromic activation from the contralateral medial lemniscus.